MODERN BIOLOGICAL INQUIRY. 287 



the present century, that the sti'ata of the earth have been successively 

 formed from fragments more or less comminuted by mechanical action, 

 more or less altered by chemical combination and molecular rear- 

 rangement. These fragments were derived from sti-ata previously 

 deposited, or from material brought up from below, or even thrown 

 down fi-om above, or from the debris of organic beings which ex- 

 tracted their mineral constituents from surrounding media. Nothing 

 new has been added, every thing is old ; only the arrangement of the 

 parts is new, but in this arrangement definite and recognizable un- 

 changed fragments of the old frequently remain. Geological observa- 

 tion is now so extended and accurate that an experienced student can 

 tell from what formation, and even from what particular locality, these 

 fragments have been derived. 



I wish to show that this same process has taken place in the or- 

 ganic world, and that by proper methods we can discover in our fauna 

 and flora the remnants of the inhabitants of former geologic times, 

 which remain unchanged, and have escaped those influences of varia- 

 tion which are supposed to account for tlie difterences in the organic 

 beings of diflerent periods. 



Should I succeed in this efibrt, we shall be hereafter enabled, in 

 groups of animals which are rarely preserved in fossil condition, to 

 reconstruct, in some measure, the otherwise extinct fauna^ and thus 

 to have a better idea of the sequence of generic forms in time. We 

 will also have confirmatory evidence of certain changes which have 

 taken place in the outline of the land and the sea. More important 

 still, we will have some indications of the time when greater changes 

 have occurred, the rock evidence of which is now buried at the bottom 

 of the ocean, or perhaps entirely destroyed by erosion or separations. 

 Of these changes, which involved connections of masses of land, no 

 surmise could be made, except through evidence to be gained in the 

 manner of which I am about to speak. 



My illustrations will naturally be drawn from that branch of 

 zoology with which I am most familiar ; and it is indeed to your too 

 partial estimate of my studies in that science that I owe the privilege 

 of addressing you on the present occasion. 



There are, as you know, a particular set of Coleoptera which affect 

 the sea-shore; they are not very numerous at any locality, but among 

 them ai*e genera which are represented in almost every country of the 

 globe. Such genera are called cosmopolitan, in distinction to those 

 which are found only in particular districts. Several of these genera 

 contain species which are very nearly allied, or sometimes in fact uii- 

 distinguishable and therefore identical along extended lines of coast. 



Now, it happens that some of these species, though they never 

 stray from the ocean-shore inland, are capable of living upon similar 

 beaches on fresh-water lakes, and a few are found in localities which 

 are now quite inland. 



